1. Field of the Invention
The present invention relates to a displacement machine which may be operated both as a pump and as a motor.
2. Description of Related Art
Displacement machines are known in a wide variety of embodiments. In displacement machines the medium is conveyed through volumes closed in on themselves. To do this, at least two adjacent working chambers are provided which are variable as to volume. The flowing back of the medium from the working chamber on the pressure side into the working chamber on the suction side is prevented by a shifting sealing line between the working chambers.
One embodiment of a displacement machine is described in published German patent document DE 43 32 540. The flying vane pump shown in this German patent document has a rotor having radially movable vane elements which are under pressure on their radially inner side. The vane elements separate working chambers that are apart in the circumferential direction. The vane elements glide along a metallic curve ring using their radially outer sides. Because of this, sealing gaps are formed between the radial outer sides of the vane elements and the curve ring. These shift together with the vane elements of the rotor, in the circumferential direction. The provision of sealing gaps assumes great manufacturing accuracy to minimize leakage, and, depending on the design variant, is a limiting factor for use in the field of high pressure, or for working media having low viscosity.
Another embodiment of a displacement machine is described in published German patent document DE 10 2004 024 641. This German patent document shows a hose (peristaltic) pump in which the medium to be conveyed is guided through a hose. In the known hose pump, the hose is supported on the one side on an press-on rod (A), and is clamped off from inside by a rotor having rollers that are circumferentially at a distance, whereby adjacent, variable volume working chambers are formed. In response to the rotation of the rotor, the sealing region moves along the hose, and thereby drives the conveyed medium forwards. The disadvantage of the known hose pump is that high contact pressures between the rotor, or rather, between the rollers and the hose have to be expended in order to prevent the flowing back of the medium that is to be conveyed. It is also a disadvantage that the hose has only a short service life because of the powerful milling effect and the compressive load that occurs.